Exec delegates to com.docker.cli if on moby context.

ExecIfDefaultCtxType delegates to com.docker.cli if on moby context.

ExecSilent executes a command and do redirect output to stdOut, return output.

IsDefaultContextCommand checks if the command exists in the classic cli (issues a shellout --help).

RunDocker runs a docker command, and forward signals to the shellout command (stops listening to signals when an event is sent to childExit).

ComDockerCli name of the classic cli binary.